Guest Post: Determining the MS-DRG

By Cheryl Ericson, MS, RN, CCDS, CDIP

Many clinical documentation improvement (CDI) specialists with clinical backgrounds are encoder dependent, trained to “code” using an encoder and taught to create a working MS-DRG based on grouper software. Many coders also rely on the encoder. However, CDI specialists and coders should understand how to manually assign a MS-DRG, too.

The basics steps for assigning a MS-DRG are:

1. Identify all the reportable diagnoses in the health record and assign their applicable ICD code (we currently use ICD-9-CM, but will transition to ICD-10-CM October 1).
2. Identify the principal diagnosis (the condition after study determined to be chiefly responsible for occasioning the admission). The remaining diagnoses are secondary diagnoses, some of which may be classified by CMS as a CC or MCC.
3. Use the Alphabetic Index of diagnoses in the DRG Expert to identify the base/medical MS-DRG, noting its Major Diagnostic Category (MDC)/body system by scanning the MS-DRGs associated with the listed pages to see which applies to the particular scenario. The MDC is necessary to assign the surgical MS-DRG when applicable.
4. Identify all reportable procedures and their associated procedure code (ICD-9-CM Volume 3 until we transition to ICD-10-PCS).

The Uniform Hospital Discharge Data Set (UHDDS) defines reportable diagnoses and procedures. Most coders and CDI specialists are familiar with the definitions associated with diagnoses, but less familiar with those associated with procedures. You should only report significant procedures. According to UHDDS, a significant procedure is one that is either:

• Surgical in nature
• Carries a procedural risk
• Carries an anesthetic risk
• Requires specialized training

In addition, UHDDS defines the principal procedure as:

• One that was performed for definitive treatment, rather than one performed for diagnostic or exploratory purposes, or was necessary to take care of a complication
• If two procedures could be principal, then select the one most related to the principal diagnosis

The UHDDS definitions of significant procedures is helpful because not all procedures will affect the MS-DRG. Some procedures won’t have any impact on the MS-DRG, some procedures will change the base medical MS-DRG, and some procedures will move the case to a surgical MS-DRG.

Procedures that are diagnostic in nature are less likely to impact the MS-DRG assignment because they are typically performed in the outpatient setting, which is why they are less likely to be the principal procedure. Also, the principal procedure is usually related to the principal diagnosis, meaning they usually can be found in the same MDC/body system. ICD-10-PCS has specific guidelines regarding the assignment of the principal procedure.

If a procedure was performed, determine if it is significant:

• If there are multiple significant procedures determine the principal procedure
• Assign the procedure code(s) and use the numeric index in the DRG Expert to see if the code is listed. If the code isn’t in the DRG Expert index of procedures, is it because of one of the two following reasons:
  
  • It is not a “reimbursable” procedure (i.e., one that will not affect the MS-DRG assignment)
  • It is a major operating room procedure